An Aswang (or Asuwang) is a vampire-like witch ghoul in Filipino folklore and is the subject of a wide variety of myths and stories. Spanish colonists noted that the Aswang was the most feared among the mythical creatures of the Philippines, even in the 16th century.[1]

The myth of the aswang is well known throughout the Philippines, except in the Ilocos region, which is the only region that does not have an equivalent myth.[2] It is especially popular in the Visayan regions such as Capiz, Iloilo, Negros, Bohol, Aklan, Antique, and Siquijor. Other regional names for the aswang include "tik-tik", "wak-wak" and "sok-sok".[citation needed]

It is a combination of a vampire and a werewolf. Sometimes this creature is called the "bal-bal" or ghoul (maninilong in Catanauan, Quezon), which replaces the cadaver with banana trunks after consumption. Aswang stories and definitions vary greatly from region to region and person to person, and no particular set of characteristics can be ascribed to the term. However, the term is mostly used interchangeably with manananggal and are also usually depicted as female.

The wide variety of descriptions in the aswang stories makes it difficult to settle upon a fixed definition of aswang appearances or activities. However, several common themes that differentiate aswangs from other mythological creatures do emerge: Aswangs are shape-shifters. Stories recount aswangs living as regular townspeople. As regular townspeople, they are quiet, shy and elusive. At night, they transform into creatures such as a cat, bat, bird, boar or most often, a dog.

They enjoy eating unborn fetuses and small children, favoring livers and hearts. Some have long proboscises, which they use to suck the children out of their mothers' wombs when they are sleeping in their homes. Some are so thin that they can hide themselves behind a bamboo post. They are fast and silent. Some also make noises, like the Tik-Tik, (the name was derived from the sound it produces) which are louder the farther away the aswang is, to confuse its potential victim; and the Bubuu, an aggressive kind of aswang that makes a sound of a laying hen at midnight. They may also replace their live victims or stolen cadavers with doppelgangers made from tree trunks or other plant materials. This facsimile will return to the victim's home, only to become sick and die. An aswang will also have bloodshot eyes, the result of staying up all night searching for houses where wakes are held to steal the bodies.

Aswangs are physically much more like humans at daytime; they only change their appearance at night when they feel they are in need of food. It has been said that if an aswang married a human, upon their wedding, his or her mate would become an aswang as well but rarely can they reproduce. The couple may hunt together at night but will go in separate directions, either to avoid detection or because they do not like to share their meal.

These creatures are not harmed by sunlight. They are daywalkers. Aswangs can also be befriended, they can talk to you like any normal human being: they laugh, cry, get mad, hurt, and feel envy. These creatures do not harm their neighbors. Neighbors were said to be exempted from their target victims for food, hence the Filipino saying, "Better an aswang than a thief." They search for food in far away places that it would not be too obvious for them. Aswangs are said to be vulnerable during daytime because during that time they do not have the excessive inhuman strength that they have in their nighttime prowl. When people know of their identity, they are hunted down and killed at the barong barong.

Like vampires, aswangs are repelled or killed by using garlic, salt, and religious artifacts (e.g. Holy water, crucifix, rosary). They are also killed using a whip made entirely of a stingray's tail, which may also be used to repel the creature ( aswangs are said to be scared of the sound made by the whip slashing through the air.) it is also said that they cannot step on holy consecrated ground. Decapitation is also a way to destroy an aswang.

Certain agimats and special prayers posted on doors may also repel aswangs. A good example of which is the orange and black bead bracelets worn by newborn babies.

It is said that to spot an aswang at daytime, look at their eyes. The person in front of you is an aswang if your reflection is upside-down. Another way of knowing is looking in a tuwad manner; that is, bending over and looking at the person from between your legs, upside-down. The person is an aswang if the image of the person is different. It is said that a person without a philtrum is an aswang. A kind of oil made by albularyos is used to detect if an aswang is near the premises. It is said that the oil will boil if an aswang is near.

An Aswang is a Wesen (creature) and the main antagonist in the Season 3, Episode 14 (Mother Dearest) of the NBC TV series "Grimm". The main characters Detectives Nick Burkhardt and Hank Griffin together with police Sergeant Drew Wu fought off an Aswang which tries to suck the fetus out of a pregnant woman who happens to be Wu's childhood friend back in the Philippines.

In a 2013 ABS-CBN TV series "Juan dela Cruz", aswangs are the main antagonist which are being hunted by the protagonist Juan who happens to be half-aswang himself.

A type of Aswang called the "Abuak" is featured in a 2011 Filipino film of the same name. Abuak can transform from human to a raven-like creature that could fly and move underground as it stalks its victim.

Aswang is featured in a 1994 Filipino film of the same name. It is about a young woman who agreed to be the wife of a rich man who lives in a mansion together with his mother, who happened to be the Aswang.

An Aswang is depicted as vampirie-like creature in new World of Darkness tabletop RPG game. Description can be found in supplement book called "Antagonists".